The present invention relates to an electronic musical keyboard instrument comprising a plurality of capture-type tone generating and keying units which may be controlled by a microcomputer interface between them and the keyboard. More particularly, the invention relates to a system for generating fill notes in a keyboard musical instrument of this type.
Present-day electronic organs include keyboards which are either of the single manual variety, as in the case of the simplest home organs, or multiple manual variety, in the case of larger console or theater organs. In a single manual organ, the keys on the right portion of the keyboard corresponding to the higher frequency notes are customarily played by the right hand of the performer, and the keys on the left portion of the keyboard corresponding to the lower frequency notes are customarily played by the left hand. In two manual organs, the upper manual is generally played by the right hand and the lower manual by the left hand. The upper manual of a console organ and the right hand portion of a single manual organ are generally referred to as the solo manual, and the lower manual of a console organ and the left hand portion of a single manual organ are generally referred to as the accompaniment manual.
In playing such an instrument, chords are formed by depressing the appropriate keys on the accompaniment manual or, in the case of a chord organ or an organ including a one finger chord feature, the chord can be played by depressing a single key, which will then automatically select the appropriate tones for the chord assigned to that key. The melody may be played either monophonically or polyphonically on the solo manual, depending on the skill of the performer. The fullness of the sound produced by playing the organ can be greatly enhanced if chords harmonically compatible with the chords played on the accompaniment manual are also played on the solo manual together with the melody note or notes. Although the full chord may not be played, it is customary to play one or two notes of the chord, known as fill notes. This technique requires a high degree of skill, however, particularly in view of the fact that the fill notes must be held as other melody notes are played by the free fingers of the right hand.
In order to enable beginner and intermediate players to achieve the same fullness of sound achieved by more advanced players who are capable of playing the fill notes manually, systems have been developed for generating fill notes of this nature automatically by mechanically or electrically coupling signals resulting from playing keys on the accompaniment manual to the tone producing circuitry such that the notes will sound as if they were played on the solo manual, preferably within an octave of the highest note played on the solo manual. The following patents are exemplary of prior art systems for automatically generating fill notes in electronic organs: U.S. Pat. Nos. 3,283,056; 3,745,225; 3,823,246; 3,247,310; 3,990,339; 3,929,051; and 4,112,802.
The disadvantage to the earlier fill note generation systems, such as those disclosed in U.S. Pat. Nos. 3,283,056 and 3,823,246 is that they require cumbersome mechanical or electronic interconnection of the keyswitches. Although this problem was alleviated by systems such as those of U.S. Pat. Nos. 3,990,339 and 4,112,802, they are more suited to automatic chord systems wherein the chord information is developed by the depression of a single key in the accompaniment manual. U.S. Pat. No. 3,929,051 discloses a system which is usable in the alternative configuration, wherein the chords must be manually played on the accompaniment manual to generate the fill note information. In this system, however, the accompaniment keys, or at least interconnected groups thereof, are scanned by the drivers which also scan the keys of the solo manual. This results in a restrictive system and the interconnection circuitry is quite unwieldy.
Earlier electronic musical keyboard instruments employed discrete keyers, which were individual circuits connected between the tone generator and the output circuitry and having a control input on which a keying envelope appears when the key corresponding to that keyer is depressed. Although discrete keyer arrangements permit a very large number of tones to be simultaneously played, they are quite costly due to the large number of keyers which must be provided. For example, for a typical sixty-one note manual having the usual number of footages, a total of ninety-six different keyers are necessary for each rank, and the ranks must be duplicated for certain voices, such as brass.
With the advent of large-scale integration techniques, a large number of keyers can be incorporated into a single chip thereby reducing the cost of the keyers and facilitating their incorporation into existing electronic organ circuitry. Keyers of this type, however, still have the drawback that a given keyer is dedicated to a certain tone thereby rendering the system somewhat inflexible, and since the keyers are an integral part of the semi-conductor chip, changes cannot easily be made without a major redesign of the chip.
Since there are only a small number of keys, generally twelve or less, which can be played at any one time, the vast majority of the keyers in a discrete system are idle at any one time so that the system has a great deal of redundancy built into it. Many years ago, it was recognized that a single keyer could be controlled to produce a wide variety of tones, and if enough of these tone generators are provided, then normal polyphonic playing can be accomplished. In order to control the individual tone generators to produce the desired tones, however, it is necessary to provide an interface between the keyboard which produces the control voltages, either as separate DC signals or a time division multiplexed signal, and the tone generator units. Since the tone generators are capable of being assigned to more than one key, it is necessary to maintain a tally of which tone generators are assigned, and in some cases, even to which key they are assigned. This enables newly depressed keys to be assigned to available tone generators and to make tone generators available as soon as they are released by lifting the keys to which they were previously assigned. Tone generator systems of this type have been used for some time, and have met with varying degrees of success.
In many assigned tone generator systems, the keydown information from the solo and accompaniment manuals is connected to the assignment system by known multiplexing techniques wherein the data is contained in a cyclically recurring time division multiplexed serial data stream. The tone generator assignment circuitry receives the serial data stream and assigns tone generator-keyer units in accordance with the keydown information contained in the data stream. Since the production of fill note data requires the analysis and processing of data relating to the highest depressed key in the solo manual and the accompaniment keys which are depressed to form the chord, difficulties may arise in capturing and assigning frequencies to the appropriate tone generator units to play the fill notes. Although logic circuitry could be utilized to analyse the solo and accompaniment data and then determine the assignment sequence for the tone generators necessary to play the fill notes, such circuitry is likely to be quite complex. A microprocessor could interface between the keyboard and the tone generator assignments, but the logic necessary to analyze the solo and accompaniment data and then generate capture commands for the tone generators assigned to the fill notes would occupy a certain portion of the memory and capacity of the microprocessor, which could better be utilized for other functions.